1. Field of the Invention
The present invention relates to cooling electronic devices, and in particular, to a cooling structure that enhances the cooling capability of high power dissipating devices and methods of manufacturing such cooling structure.
2. Description of Related Art
Modern electronic devices, such as those having increased power densities, operating frequencies and current leakages, as well as devices having small cooling fluid thermal budgets or having very high average power flux, are continually requiring improved thermal structures for providing enhanced thermal capabilities. For instance, in an electronic device having a high average power flux, a high power hot spot may dissipate 200 to 500 W/cm2, while a very high power hot spot may dissipate more than 500 W/cm2. Under such processing conditions, conventional thermal technologies, such as heat spreaders, heat sinks, and associated thermal interfaces, will undesirably increase the power flux and generate high thermal gradients along the cooling axis.
To address the problems associated with these high thermal gradients, single-phase fast-forced convection and/or two-phase evaporation based devices with a circulating fluid have been introduced in the art. These types of cooling devices commonly include a body having a number of liquid jets that impinge a target surface, along with lateral drains for removing spent fluid from between the cooling device body and the target surface. In this manner, the high kinetic energy of the array of fluid jets provide fluid in close proximity to the surface for enabling a high cooling rate of the target, particularly at the location where the jets impinge. However, this high heat/cooling transfer rate decreases rapidly in areas of the surface not residing directly below the surface area being impinged, which leads to uneven cooling of the target. Also, the lateral drains remove spent fluid in a radial flow pattern away from a fluid jet with a maximum velocity at the periphery of the jet array, and as such, are insufficient for cooling high power flux situations.
Current fluid jet arrays also require a high fluid flow rate, which in turn, results in an undesirable increase in pressure drop on the cooler. Known circulating cooling fluid solutions also have a maximum operating pressure for preventing fluid leakage and mechanical damage to the system. Since increasing the fluid velocity typically increases cooling capabilities, an increase in fluid velocity in conventional cooling devices to provide high cooling capabilities, such as above 400 W/cm2, would deleteriously generate high operating pressures that exceed the device pressure limits. As such, the pressure drop required to operate modern electronic devices having high power flux situations limits the extendibility of conventional cooling devices.
Therefore, a need continues to exist in the art for improved thermal assemblies, and methods of making such assemblies, that maximize the heat transfer rate of fluid jet arrays for cooling/heating components having high power flux, while simultaneously controlling the fluid pressure drop in the cooling assemblies.